- 1 year ago
how to catch or __except when double free runtime error (HeapAlloc)
To catch or handle a runtime error like a double-free error in the HeapAlloc
function, you can use structured exception handling (SEH) in Windows. Here's an example of how you can catch the error using the __try
and __except
keywords:
cpp#include <Windows.h>
#include <iostream>
int main() {
__try {
LPVOID memory = HeapAlloc(GetProcessHeap(), 0, sizeof(int));
// Simulate a double-free error
HeapFree(GetProcessHeap(), 0, memory);
HeapFree(GetProcessHeap(), 0, memory);
}
__except (EXCEPTION_EXECUTE_HANDLER) {
std::cout << "Caught exception: double-free error" << std::endl;
}
return 0;
}
In the code above, we allocate memory using HeapAlloc
and then simulate a double-free error by calling HeapFree
twice on the same memory block.
The __try
block is used to wrap the code that may generate an exception. The __except
block follows the __try
block and is executed only if an exception occurs within the __try
block.
The EXCEPTION_EXECUTE_HANDLER
is a constant that specifies the exception handling behavior. In this case, it directs the exception handler to execute the code within the __except
block.
In the example, when the double-free error occurs, the exception is caught by the __except
block, and the message "Caught exception: double-free error" is displayed.
It's important to note that SEH can only handle structured exceptions like access violations or arithmetic errors. Double-free errors are typically not structured exceptions and may not be caught by SEH. In such cases, you may need to use other memory management techniques and debugging tools to detect and prevent double-free errors.